The narrow-leaved purple coneflower (Echinacea angustifolia) produces echinacin and related compounds in the root, which are known to have immune and curative properties against viral, fungal, and bacterial infections. In recent years, cultivation of this species has increased in response to growing market demand for natural medicinal remedies. The objective of this study was to determine the influence of gibberellic acid and light on the germination of E. angustifolia seeds. Seeds soaked for 24 h in 0, 1, 5, 10, 50, 100, 250, 500 or 1000 mg/L GA3 solution were germinated on Whatman #1 filter paper inside petri dishes at 22 °C with or without light (80 μmol·m-2·s-1) for 21 days. The seeds germinated poorly in dark with the final percent germination range from 10% (GA3 1000 mg/L) to 36% (GA3 250 mg/L). Under light, seed germination showed a quadratic response (r = 0.84) to GA3 concentration. Percent germination exceeded 90% at 10, 50, and 100 mg/L GA3 with the mean time (T50) to germinate varying at 10.5, 11.7, and 13.3 days, respectively, under light. Seed germination under light was <10% when treated with 500 and 1000 mg/L GA3. In general, seed germination was best when treated with 10 or 50 mg/L GA3 under light. Results of this research may well be used in enhancing seed germination during field establishment of E. angustifolia.
The biomass yield, transpiration rate, and chlorophyll contents in Cymbidium goeringii plants grown under various light, temperature, and humidity conditions were investigated. Two-year-old plants potted in pine-bark medium were grown for 12 weeks during the summer months in polyethylene film-covered mini-greenhouses having four different environmental conditions: a) closed house (CH) with high humidity (95.1% RH), high light (800 μmol·m–2·s–1) and high temperature (37.5 °C), b) ventilated house (VH) with low humidity (41.4% RH), high light (800 μmol·m–2·s–1), and medium temperature (31.5 °C), c) shaded closed house (SCH) with high humidity (91.0% RH), low light (110 μmol·m–2·s–1) and medium temperature (33.3 °C), and d) shaded ventilated house (SVH) with medium humidity (61.5% RH), low light (110 μmol·m–2·s–1) and low temperature (30.5 °C). Plants grown in CH produced leaf chlorosis with 50% shorter leaves and 40% lower relative growth rate (7.9 mg/g fresh weight per day) compared to plants grown in SVH. Cymbidium plants grown in SCH or SVH showed higher leaf and root dry weights as compared to those grown in CH or VH. Leaf chlorophyll-a and -b contents as well as carbohydrate levels were the highest in plants grown in SVH, indicating the benefits of shading and ventilation. The rate of transpiration showed a quadratic response to increasing levels of leaf temperature (r2 = 0.81), wind velocity (r2 = 0.82), and vapor pressure deficit (VPD, r2 = 0.91). Regression analysis revealed that the maximum transpiration rate occurred at 25.4 °C leaf temperature, 2.1 m/s wind velocity, and 2.3 kPa VPD in this experiment.
The influence of calcium nitrate fertilization on the storage characteristics of carrot (Daucus carota) roots was investigated. Plants of `Navajo' carrots grown under irrigation were sprayed with a 2% solution of Ca(NO3)2 4H2O at a rate of 50 kg/ha Ca 10 days before harvest. Quality of carrot roots stored at 5 °C was evaluated monthly for sweetness, tissue electrolyte leakage, disease development and visual characteristics. For disease development, the crown portion of the carrot roots was inoculated with an ascospore solution (2 × 109 spores/mL) of white mold (Sclerotinia sclerotiorum) before storage. When determined after 1 month of storage, percent tissue electrolyte leakage in the Ca-treated carrots decreased 52% as compared to that obtained from the control. Sugar contents of the cortex and xylem tissues were not affected by calcium nitrate fertilization. Changes in other quality parameters of carrot roots for an extended storage period, including white mold development, will be presented. Initial findings of this research suggest that foliar calcium feeding at the final stage of plant growth may enhance the quality of carrot roots during storage.
The influence of calcium (Ca++) nutrition on the growth and root tissue electrolyte leakage (EL) of carrot (Daucus carota) was investigated using a hydroponic culture system. Seedlings of `Navajo' carrot were grown for 10 weeks with roots submersed in hydroponic nutrient solutions containing 0, 0.1, 1, 2, 4, or 8 meq/L Ca++. The nutrient solution was replenished weekly with its pH maintained at 5.8 for the entire experimental period. The tap root lengths increased as solution Ca++ concentration increased. The diameter and fresh and dry weights of the tap roots increased as Ca++ concentration increased up to 4 meq/L, and then decreased at 8 meq/L Ca++. The root and petiole concentrations of sugar, potassium, and nitrate were unaffected by changes in nutrient solution Ca++ levels. The tissue EL, when tested for the stored roots, decreased as solution Ca++ concentration increased (r = 0.602). Results of this experiment suggest that calcium nutrition is essential for maintaining cell wall integrity in hydroponically grown carrot roots.